endocrine regulation

7/31/2019 Endocrine Regulation

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ENDOCRINEREGULATION

Theendocrinesystemregulates:

- growth/development

- responsetostress- reproduction- fluidbalance- otherphysiologicalprocesses

ThetissuesandorgansoftheendocrynesystemsecreteHORMONES,Chemicalsmessengersthatsignalothercells.

Thehypothalamusandthepituitaryglandregulatemanyofthesehormones

TheendocrinesystemisaCollectionofcells,tissuesandorgans+spcializedendocrineglands,thatproduceandsecretehormones,

ChemicalsMessengersthatregulatemanyphysiologicalprocesses.

Hormone(toexcite)exciteorstimulatechangesinspecifictissues.

Differencesglands

- ExocrineglandsReleasetheirsecretionsintoducts

e.g.sweatglands/gastricglands

- Endocrineglands

Havenoductsandsecretetheirhormonesintothesurroundingintersitialfluidorblood

Theyare10endocrineglands+specializedcellsinthedigestivetract,heart,kidneyandmanyotherpartsofthebody.


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Hormones

Transportedbythebloodandproduceacharacteristicresponsealtertheyreachtargetcellsandbindwithspecificreceptors.

Targetcells:cellsinfluencedbyaparticularhormone

Maybeinanotherendocrineglandordifferentorgan

Maybefarawayfromtheendocrinegland.

Endocrinesystemandnervoussystem

BothofthemworkcloselytomaintainHOMEOSTASIS(steadystateofthebody)

ENDOCRYNESYSTEM NERVOUSSYSTEM

Signalsmuchtargetcells Signalsmuscles/glands(endocrine

glands)

Respondsmoreslowly

(butLangerlasting)

Respondsrapidly

Helpsregulatemanyendocrineresponses

Producessomehormones

(neurotransmitters)

SometimesbothfunctionsBlur:thesamesignalmoleculecanfuncitionas

eitherneurotransmitterorahormone

e.g.Norepinephrine


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Homeostasis

Whenadisorderordiseaseaffectsanendocrinegland,therateofsecretionmaybeabnormal.

Hyposecretion:abnormalreduceoutputandtargetcellsaredeprivedofneededstimulation. Hypersecretion:abnormallyincreasedoutputandthetargetcellsmaybeoverstimulated.Allthisleadsinmalfunctionandlossofhomeostasis.

Negativefeedbacksystems

Regulateendocrineactivity.

Hormonemoleculescontinuouslymoveoutofthecirculationandbindwithtargetcells.

- Liver:removesthem(inactivates)- Kidneys:excretethem

HormoneproductionisregulatedbytheNSandEndocrineglands.

MostendocrineactionisregulatedbyNEGATIVEFEEDBACKSYSTEMS:

self-regulatingresponsestochangesexperiencedbyasystemororganism,usuallyduetoexternalinfluences.Resultinrestoringthesystem

toitspreviousundisturbedstate,ormitigatingtheeffectsoftheinitialchange.Itisthischaracteristicof"negating"theimpactofchanges

whichdefinessuchoperationsas"negativefeedbackmechanisms".

e.g.parathynoidglands:regulatethecalciumconcentrationoftheblood

Whencalciumconcentrationiseithertoohighortoolow,negativesystemrestoreshomeostasis

-calcium:parathyroidglandreleasesmoreparathyroidhormones(increases)


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+calcium:parathynoidglandsslowtheiroutputofhormone.

BothresponsesarenegativefeedbackSystems.

Groupsofhormones

Hormonesbelongtooneofthesegroups:

1. fattyacidderivatives

Prostaglandins:ininsects

2. steroids

- adrenalcortex- testis- ovary- placentasecretesteroidhormonessynthesizedbycholesterol.

Examplesofsteroidhormones:

cortisol(secretedadrenalcortex)

testosterone(secretedbythetestis)

progesterone/estrgeno(secretedbytheovary)

3. aminoacidderivatives

simplesthormones

thyroidhormonesT1/T4(synthesizedfromtheaminoacidthetyrosineandIodine)

Epinephrine(adrenaline)/norepinephrine(alsoderivedfromtyrosine)


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Melatonin(synthesizedaminoacidtryptophan)

4. peptidesorproteins

largesthormones/peptidehormones/watersoluble

Neuropeptides:largeGroupofsignalingmoleculesproducedbyneurons

oxitocina/antidiuretichormone(ADH)areshortneuropeptides

Glucagon/secretin/calcitoninalongpeptides(30aminoacids)

Insulinsmallprotena(2peptidechainsbydissulfideBonds)

Endocrinesignaling

Hormonessignaltheirtargetcellsby:

Classicalendocrinesignaling

Hormonesaresecretedbyendocrineglandsandaretransportedbythebloodtotargetcells.

- Steroidhormones- Thyroidhormonesare;bothtransportedboundtoplasmaproteins

-Peptidehormones(watersoluble)aredisolvedintheplasma..

Neuroendocrinesignaling

Nueroendocrinecells:linkbwNS-ES

Neuroendocrinecellssecreteneurohormones:thesehormonesaretransporteddownaxonsandthensecretedandtransportedbytheblood.


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Autocrinesignaling

Ahormone(orothersignalmolecule)issecretedintotheintersitialfluidandthenactsontheverycellthatproduceit.

e.Estrogen:functionsasaclasssicalhormone,canalsoexertanautocrineeffectthatstimulatesadditionalestrgenosecretion.

Paracrinesignaling

Ahormone(orothersignalmolecule)difusesthroughintersitialfluidandactsonnearbytargetcells.

Estrgenocanalsoactthisway.


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GLAND HORMONE TARGETTISSUE ACTIONS

HYPOTHALAMUS

Releasingandinhibitinghormones

Anteriorpituitary

Regulatesecretionofhormonesby

theanteriorpituitary

POSTERIORPITUITARY

Storageandreleaseof

hormonesproducedbyhypothalamus

Oxytocin

Antidiuretichormone

(ADHorvasopressin)

Uterus

Mammarygland

Kidneys(collectingducts)

Stimulatecontraction

Stimulateejectionofmilkintoducts

Stimulatereabsorptionofwater

ANTERIORPITUITARY

GroWthhormone(GH)

Orsomatotropin

(anabolichormone)

Prolactin

Melanocyte-stimulatinghormone(MSH)

General

Mammaryglands

Pigmentocells(skin)

Stimulatesgrowthofskeleton/muscles

Stimulatesmilkproduction

Stimulatesmelaninproduction


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ANTERIORPITUITARY

Thyroidstimulatinghormone(TSH)

Adrenocorticotropichormone(ACTH)

Gonadotropichormones

FSH/LH

Thyroidgland

Adrenalcortex

Gonads

Stimulatessecretionofthyroid

hormones,helpsregulatingbone

remodeling

Stimulatessecretionofadrenal

corticalhormones

Stimulategonadfunctionandgrowth

THYROIDGLAND

.

Thyroxine(T4)

Triiodothyrionine(T3)

Calcitonin

General

Bone

Stimulatemetabolicrate

RegulateEmetabolismo

LowersbloodCa+level

(decreases)

PARATHYROIDGLAND

Parathyroidhormone

(PTH)

Bone

Kidney

Digestivetract

RegulatesbloodCa+level

(antagonistaofCalcitonin)

StimulatesCareleasefromthebones

----------------------------------

Note:duringpregnancy/growth

periodchildhoodCaveryimportant


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PARATHYROIDGLAND

Parathyroidhormone(PTH)

Bone

KidneyDigestivetract

RegulatesbloodCa+level

(antagonistaofCalcitonin)

StimulatesCareleasefromthebones

----------------------------------

Note:duringpregnancy/growth

periodchildhoodCaveryimportant

Roleofvitamina3D.

PANCREAS

Insulin

Glucagon

General

Liver,adiposetissue

Lowersbloodglucoseconcentration

Raisesbloodglucoseconcentration

ADRENALMEDULLA

Epinephrine

Nonepirephrine

Muscle

Bloodvessels

Liver

Adiposetissue

Helpbodytocopewithstress

Increasemetabolicrate

RaisebloodglucoselevelIncreaseheartrate/bloodpressure

ADRENALCORTEX

Mineralcorticoids

Kidneytubules

MaintainNa/Kbalance


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PositionoftheEndocrineglands

Thehypothalamusandpituitarycontrolalargepartoftheendocrinesystem.

Thethyroidisintheneckjustbelowthelarynx.Theparathyroidglandsareonthebackofthethyroid.

Thethymusisanteriorandsuperiortotheheart.

Theadrenalglandsaresuperiortothekidneys.Thepancreasisinferior/posteriortothestomach.

Theovariesareintheabdominopelviccavity.

Thetestiesareinthescrotum,descendedfromthepelviccavity.

TESTIS

Testosterone

General

Reproductivestructures

Developessexcharact

Promotesspermatogenesis


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The major human endocrine glands include:

1. thehypothalamusandpituitaryglandThepituitaryglandiscalledthemaster

glandbutitisunderthecontrolofthe

hypothalamus.Together,theycontrol

manyotherendocrinefunctions.They

secreteanumberofhormones,

especiallyseveralwhichareimportant

tothefemalemensturalcycle,

pregnancy,birth,andlactation(milkproduction).Theseincludefollicle-

stimulatinghormone(FSH),which

stimulatesdevelopmentandmaturation

ofafollicleinoneofawomansovaries,andleutinizinghormone(LH),which

causestheburstingofthatfollicle(=

ovulation)andtheformationof

acorpusluteumfromtheremainsof

thefollicle.

Thereareanumberofother

hypothalamusandpituitaryhormones

whichaffectvarioustargetorgans.

Onenon-sexhormonesecretedbytheposteriorpituitaryisantidiuretichormoneorADH.Thishormonehelpspreventexcesswaterexcretionbythekidneys.EthanolinhibitsthereleaseofADHandcan,thus,causeexcessive

waterloss.Thatsalsopartofthereasonwhyagroupofcollegestudentswhogooutforpizzaandapitcherofbeer

needtomakefrequenttripstotherestrooms.Diureticsarechemicalswhichinterferewiththeproductionofor

actionofADHsothekidneyssecretemorewater.Thusdiureticsareoftenprescribedforpeoplewithhighblood


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pressure,inanattempttodecreasebloodvolume.

Anothergroupofnon-sexhormonesthatmanypeoplehaveheardofistheendorphins,whichbelongtothecategory

ofchemicalsknownasopiatesandservetodeadenourpainreceptors.Endorphins,whicharechemicallyrelatedto

morphine,areproducedinresponsetopain.Thenaturalresponsetorubaninjuredarea,suchasapinchedfinger,

helpstoreleaseendorphinsinthatarea.Peoplewhoexercisealotandpushtheirbodiesuntilithurtsthereby

stimulatetheproductionofendorphins.Itisthoughtthatsomepeoplewhoconstantlyover-exerciseandpush

themselvestoomuchmayactuallybeaddictedtotheirownendorphinswhichthatsevereexerciseregimereleases.

2. thethyroidgland

Thyroidhormonesregulatemetabolism,thereforebodytemperatureandweight.Thethyroidhormonescontain

iodine,whichthethyroidneedsinordertomanufacturethesehormones.Ifapersonlacksiodineinhis/herdiet,the

thyroidcannotmakethehormones,causingadeficiency.Inresponsetothebodysfeedbackloopscallingformore

thyroidhormones,thethyroidglandthenenlargestoattempttocompensate(Thebodysplanhereisifitsbiggerit

canmakemore,butthatdoesnthelpifthereisntenoughiodine.).Thisdisorderiscalledgoiter.Dietarysourcesof

iodineincludeanyoceanfoodsbecauseocean-dwellingorganismstendtoaccumulateiodinefromtheseawater,

andwouldincludefoodslikeoceanfish(tuna)andseaweedslikekelp.Becauseofthis,peoplewholiveneartheoceandonothaveasmuchofaproblemwithgoiteraspeoplewholiveinlandanddonthaveaccesstothesefoods.Tohelp

alleviatethisprobleminourcountry,ourgovernmentbeganaprogramencouragingsaltrefinerstoaddiodinetosalt,

andencouragingpeopletochoosetoconsumethis iodizedsalt.

3. thepancreas

Thisorganhastwofunctions.Itservesasaductedgland,secretingdigestiveenzymesintothesmallintestine.The

pancreasalsoservesasaductlessglandinthattheisletsofLangerhanssecreteinsulinandglucagontoregulate

thebloodsugarlevel.The -isletcellssecreteglucagon,whichtellsthelivertotakecarbohydrateoutofstorageto

raisealowbloodsugarlevel.The -isletcellssecreteinsulintotellthelivertotakeexcessglucoseoutofcirculation

tolowerabloodsugarlevelthatstoohigh.Ifapersonsbodydoesnotmakeenoughinsulin(and/orthereisareducedresponseofthetargetcellsintheliver),thebloodsugarrises,perhapsoutofcontrol,andwesaythatthe

personhasdiabetesmellitus.


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4. theadrenalglands

Thesesitontopofthekidneys.Theyconsistoftwoparts,theoutercortexandthe

innermedulla.Themedullasecretesepinephrine(=adrenaline)andother

similarhormonesinresponsetostressorssuchasfright,anger,caffeine,orlow

bloodsugar.Thecortexsecretescorticosteroidssuchascortisone.

Corticosteroidsarewell-knownasbeinganti-inflammatory,thusareprescribed

foranumberofconditions.However,thesearepowerfulregulatorsthatshouldbe

usedwithcaution.Medicinaldosesaretypicallyhigherthanwhatyourbody

wouldproducenaturally,thusthepersonsnormalfeedbackloopssuppress

naturalsecretion,anditisnecessarytograduallytaperoffthedosagetotrigger

theadrenalglandstobeginproducingontheirownagain.Becausethe

corticosteroidssuppresstheimmunesystem,theirusecanleadtoincreased

susceptibilitytoinfections,yetphysicianstypicallyprescribethemforpeoplewhoseimmunesystemsarehardatworktryingtofightoffsomepathogen.For

example,backwhenIwasingradschool,Iwasdiagnosedwithmono,andthecampusdoctorprescribedpenicillinandcortisone.Sincemonoisavirusandpenicillinonlyiseffectiveagainstsome

bacteria,aboutallitdidwaskilloffthefriendlybacteriainmybody,thereforecausingmetodevelopabadcaseof

thrush.Atthesametime,thecortisonewassupressingmyimmunesystemsomybodycouldnotasefficientlyfight

offthemonoandthethrush.Peoplewithhighbloodpressureshouldbeleeryoftakingprescriptioncorticosteroids:

theyareknowntoraisebloodpressure,thuscancausethingslikestrokes.Mymother-in-lawhadhighbloodpressure

andwasbeingtreatedwithdiuretics.Herphysicianalsohadheronlargedosesofcortisoneforherarthritis.Whilehe

wasonvacation,shestartedhavingsignificantbackpainandwasreferredtoanorthopedicsurgeon.Thisman

decidedthebackpainwasjustduetoarthritis,andwithoutcarefullycheckingonwhatdosageshewasalready

taking,prescribedmorecortisone.Simultaneously,becauseofdifficultywalkingduetoherarthritis,shedecidedtodecreasetheamountofdiureticsshewastakingsoshedidnthavetomakeasmanylongtripstotheotherendof

thehouse.Thecombinationoflowereddoseofdiureticsandhighdoseofcortisoneraisedherbloodpressuretothe

pointwhereabloodvesselinherbrainburst,causingastroke.WhentheEMTstookherbloodpressure,asIrecallthe

systolicwaswayover200mmHg.


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5. thegonadsorsexorgans

Inadditiontoproducinggametes,thefemaleovariesandmaletestes(singular=testis)alsosecretehormones.

Therefore,thesehormonesarecalledsexhormones.Thesecretionofsexhormonesbythegonadsiscontrolledby

pituitaryglandhormonessuchasFSHandLH.Whilebothsexesmakesomeofeachofthehormones,typicallymale

testessecreteprimarilyandrogensincludingtestosterone.Femaleovariesmakeestrogenandprogesteronein

varyingamountsdependingonwhereinhercycleawomanis.Inapregnantwoman,thebabysplacentaalsosecretes

hormonestomaintainthepregnancy.

6. thepinealglandThisglandislocatednearthecenterofthebraininhumans,andisstimulatedbynervesfromtheeyes.Insomeother

animals,thepinealglandisclosertotheskinanddirectlystimulatedbylight(somelizardsevenhaveathirdeye).

Thepinealglandsecretedmelatoninatnightwhenitsdark,thussecretesmoreinwinterwhenthenightsarelonger.

Melatoninpromotessleep(makesyoufeelsleepy).Italsoaffectsreproductivefunctionsbydepressingtheactivityof

thegonads.Additionally,itaffectsthyroidandadrenalcortexfunctions.Insomeanimals,melatoninaffectsskin

pigmentation.Becausemelatoninproductionisaffectedbytheamountoflighttowhichapersonisexposed,thisis

tiedtocircadianrhythm(havinganactivitycycleofabout24hours),annualcycles,andbiologicalclockfunctions.SADorseasonalaffectivedisorder(syndrome)isadisorderinwhichtoomuchmelatoninisproduced,

especiallyduringthelongnightsofwinter,causingprofounddepression,oversleeping,weightgain,tiredness,and

sadness.Treatmentconsistsofexposuretobrightlightsforseveralhourseachdaytoinhibitmelatoninproduction.It

hasalsobeenfoundthatmelatoninlevelsdrop75%suddenlyjustbeforepuberty,suggestingtheinvolvementof

melatoninintheregulationoftheonsetofpuberty.Studieshavebeendoneonblindgirls(withaformofblindnessin

whichnoimpulsescantraveldowntheopticnerveandreachthebrainandpinealgland),whichshowedthatthesegirlstendedtohavehigherlevelsofmelatoninforalongertime,resultinginadelayintheonsetofpuberty.While

someolderpeople,whodontmakeverymuchmelatonin,thusdontsleepwell,mightbenefitfromamelatonin

supplement,Imskepticaloftherecentmelatonincrazeinthiscountry.WhensomanypeopleapparentlyaresufferingfromSAD,Iquestionthewisdomofpurposlyingestingmoremelatonin,especiallysincethepinealglandis

oneoftheleast-studied,least-understoodoftheendocrineglands.


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7.TheThymusGland

7.Thisglandislocatedbehindthebreastbone.Itproducesthehormonethymosin.Thishormonecauseswhitebloodcells(lymphocytes)

tobecomematureandactive.Thesebloodcells,aspreviouslydiscussedintheBloodweb

Local regulators are hormones with target cells nearby or adjacent to the endocrine gland in question. For example,

neurotransmitters are secreted in the synapses of our nervous system and their target cells are in the same synapses.


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ENDOCRINE DISORDERS

Adrenal insufficiency. The adrenal gland releases too little of the hormone cortisol and sometimes, aldosterone. Symptoms include fatigue, stomach

upset,dehydration, and skin changes.Addison's disease is a type of adrenal insufficiency.

Cushing's disease. Overproduction of a pituitary gland hormone leads to an overactive adrenal gland. A similar condition called Cushing's syndrome

may occur in people, particularly children, who take high doses of corticosteroid medications.

Gigantism (acromegaly) and other growth hormone problems. If the pituitary gland produces too much growth hormone, a child's bones and body

parts may grow abnormally fast. If growth hormone levels are too low, a child can stop growing in height.

Hyperthyroidism. The thyroid gland produces too much thyroid hormone, leading to weight loss, fast heart rate, sweating, and nervousness. The most

common cause for an overactive thyroid is an autoimmune disorder called Grave's disease.

Hypothyroidism. The thyroid gland does not produce enough thyroid hormone, leading to fatigue, constipation, dry skin, and depression. The

underactive gland can cause slowed development in children. Some types of hypothyroidism are present at birth.

Hypopituitarism. The pituitary gland releases little or no hormones. It may be caused by a number of different diseases. Women with this condition may

stop getting their periods.

Multiple endocrine neoplasia I and II (MEN I and MEN II). These rare, genetic conditions are passed down through families. They cause tumors of the

parathyroid, adrenal, and thyroid glands, leading to overproduction of hormones.Polycystic ovary syndrome (PCOS). Overproduction of androgens interfere with the development of eggs and their release from the female ovaries.

PCOS is a leading cause of infertility.

endocrine regulation

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